1. Field of the Invention
The present invention relates to a linear imaging optical system in which light flux from a light source is formed as a linear image, and the light flux in the form of the liner image is made incident on a reflection surface of a light deflector in the optical scanning system.
2. Description of the Related Art
In a laser printer or other such scanning optical systems, in order to correct facet-error of a reflection surface of a polygon mirror (a light deflector), light flux from a light source is formed as a linear image, and the light flux in the form of the linear image is made incident on the light deflector for scanning. In such a scanning optical system, a linear image forming single lens element has been known. More concretely, a linear image forming single lens element is a single lens element having the collimating function for making diverging light flux from a light source parallel, and the function of a cylindrical lens element for forming a linear image. However, in a linear image forming single lens element of the prior art, the correcting of aberrations has disadvantageously been insufficient on cross-sections which are inclined with respect to the direction of the linear image and the direction perpendicular to the linear-image. It has also been known that a linear image forming single lens element of this type has conventionally employed an aspherical surface for the purpose of correcting various aberrations. A complex configuration of an aspherical surface could be designed to have sufficient optical performance; however, actual optical performance of the lens element is not always satisfactory due to production error, because such an aspherical surface has high decentering sensitivity.